Description

The black guillemot or 'tystie' is a circumpolar species,
concentrated around the North Atlantic, Barents Sea, Baltic and
smaller numbers around the Chukchi Sea in northern Alaska and
north-eastern Siberia. Approximately half of the UK's population
breeds around the Northern Isles, with the remainder confined
mainly to the coasts and islands of north and west Scotland. Their
distribution within the core range is determined by the
availability of suitable nest cavities that are safe from land
predators such as rats Rattus sp., American mink
Neovison vison, stoats Mustela erminea and
otters Lutra lutra. Between censuses in 1969-70 and
1985-91, there was an expansion in the range of black guillemots,
in particular the colonisation of new sites around the Irish Sea,
including man-made structures (e.g. harbour walls, jetties, piers),
and into north-east Scotland.

The species is one of the more problematic seabirds to survey.
It tends to breed away from the large seabird cliff colonies and
prefers small rocky islands and low-lying, indented stretches of
rocky coast. Nests are hidden in rock crevices and under boulders,
which makes them extremely difficult to census during the breeding
season (see below).

Conservation status

Black guillemot is currently identified as a conservation
priority in the following:

International importance

The UK population figure (rounded to the nearest hundred) was
derived from data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E.
(eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also the
source of figures for the Biogeographic and World populations.

UK population estimates and change 1969-2002 (census
data)

During Operation Seafarer (1969-70), counts were conducted along
with other cliff-nesting seabirds during June. At this time of
year, black guillemots are often inconspicuous. Operation Seafarer
therefore underestimated the population by an unknown number.
Between 1982 and 1991, as part of the SCR Census, a survey of the
number of adult black guillemots was conducted between late March
and early May prior to the breeding season. Surveys were carried
out between 06.00 – 09.00 BST when adults congregate close
inshore for courtship and mating. Such counts have been found to be
the most repeatable and accurate way of assessing population
size. A pre-breeding survey was repeated during Seabird
2000 throughout Britain and Northern Ireland, and thus,
provided the first opportunity to examine changes in the
population of black guillemots in many areas since 1982-91.
The main reason for this is that the spatial scales at which
counts were conducted during the SCR Census and Seabird 2000 were
highly compatible.

Operation Seafarer

(1969-70)

Seabird Colony Register

(1982-91)

Seabird 2000

(1998-2002)

UK Population estimate (Individuals)

N/a

37,745

38,714

% change since previous census

N/a

N/a

+3

For census results for individual countries and Ireland, the
Channel Islands and the Isle of Man see under relevant
sections below.

Distribution/abundance

The Seabird
2000 census provides the most comprehensive recent
assessment of the distribution and abundance of breeding seabirds.
Numbers of black guillemot found in different regions,
and a map showing the locations and size of colonies, is provided
in the Seabird 2000 black
guillemot results page (PDF, 2.2 mb).

An
interactive map is available on the NBN Gateway, where you can
filter to display only the Seabird 2000 data. For more
recent, but less comprehensive, coverage view the distribution on
the NBN with all available contributing datasets.

Annual abundance and productivity by geographical area

With reference to the regional
accounts below please note the following.

Breeding abundance:
graphs of abundance index with 95% confidence limits are only shown
for a region where the trend produced has been deemed accurate
(see
methods of analysis). Where a trend was thought to be
inaccurate, graphs of abundance at major colonies in a
region may be shown instead, particularly if such colonies
hold greater than 10% of the regional population,
are monitored frequently and may thus help illustrate regional
population fluctuations outwith national censuses.
Occasionally, too few data have been collected regionally to
produce either of these.

Productivity: graphs
of productivity are only shown if analysis of breeding
success data produced a significant result for regional and/or
year effects (again see
methods of analysis). If results were not significant,
then a regional mean productivity value is given.
However, on some occasions, too few data are
available from which to provide a meaningful average.
Furthermore, for 11 species where the quality of monitoring data
available was considered high, population viability analysis
was undertaken at the UK level and the results of this are
also reported.

Breeding abundance

The UK annual sample of black guillemots is small though appears
to be representative of the population as a whole.
Abundance derived from the sample of colonies
monitored as part of the SMP has been generally
stable since 1987, normally fluctuating between 52-67% of the 1986
index, although has appeared to be increasing in recent
years. Census results also indicate that the UK population
changed little (+3%) between the SCR and Seabird 2000 (no
comparable data are available from Operation Seafarer).

Productivity

The productivity of black guillemots derived from regularly
monitored colonies in the UK (mostly located in
Orkney, and in Co. Down) showed no statistically significant
variation over time. On average, productivity was approximately
1.01 chicks fledged per pair per year between 1986 and 2014. No
productivity data for 2015 was submitted to the SMP.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

37,172

37,505

% change since previous
census

N/a

N/a

<+1

Breeding abundance

The total population of the black guillemot in Scotland
was stable between the Seabird Colony Register and Seabird 2000
censuses -c.37,000 individuals were recorded
in each census. The abundance index above, based on the SMP sample
shows an increasing trend since Seabird 2000. However, most
data collected annually are from colonies in Shetland with few
data from sites along other parts of the Scottish coastline.
The disparity between the high abundance value for 1986 and
subsequent fall in 1987, after which the index was reasonably
stable for almost 20 years, is probably due to fewer than
usual colonies being monitored in 1986, and hence a
potentially unrepresentative sample, although the number of sampled
colonies in any year is never large. The abundance index
increased slowly since 2008 but fell to 35% below the 1986 baseline
in 2015.

Productivity

The productivity of black guillemots derived from regularly
monitored colonies in Scotland (mostly located in Orkney and
Shetland) showed no statistically significant variation over time.
On average, productivity was approximately 1.01 chicks fledged per
pair per year between 1986 and 2012. No productivity data has
been collected since 2015.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

14

7

% change since previous
census

N/a

N/a

-50

Breeding abundance

England holds only a few breeding black guillemots all located
at St. Bee’s Head (Cumbria). Fourteen individuals were counted
during the Seabird Colony Register, but numbers had halved by
Seabird 2000. Ten individuals were recorded in 2011 and
2012, nine in 2013 with only six recorded in 2014. No data was
collected in 2015.

Productivity

No systematic data on the productivity of black
guillemots in the small population in England have been submitted
to the SMP.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

26

28

% change since previous
census

N/a

N/a

+8

Breeding abundance

Only 28 black guillemot individuals were counted in Wales during
Seabird 2000, mostly around Anglesey (Gwynedd), a
similar number to that found during the Seabird Colony
Register. No sites of any size are monitored frequently so the
current status of the population is unknown.

Productivity

No systematic data on the productivity of black
guillemots in Wales have been submitted to the SMP.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

533

1,174

% change since previous
census

N/a

N/a

120

Breeding abundance

In Northern Ireland, black guillemots increased by 120% between
the Seabird Colony Register and Seabird 2000 to 1,174
individuals, probably as a result of increased use of man-made
structures for nest sites. Habitat such as harbour walls and piers
provided important nesting sites, and it was estimated such habitat
held over twice as many nesting black guillemots during Seabird
2000 than it did during the SCR; this equated to
an estimated 22% of the national population1.
Extensive survey work was carried out at 36 colonies in April
2014 which held an estimated 80% of the country's population
during Seabird 20002. The total recorded, at 908
individuals, was 8% less than 990 individuals recorded in the
same areas during Seabird 2000. It also appears that some
distributional shift has occurred as 102 birds were recorded at
sites which apparently held no birds during Seabird 2000.

Productivity

The productivity of black guillemots in Northern Ireland
shows no statistically significant variation over time. On
average 0.98 chicks were fledged per pair per year at
monitored colonies between 1986 and 2015.

Close study of a colony at Bangor Marina (Co. Down, where most
pairs nest in specially provided holes and nest boxes) has revealed
losses of eggs to children and predation of eggs and chicks by
brown rats, herring gulls and domestic/feral cats
Felis catus. Gulls have also been seen removing
sitting adults, although this has been mitigated against by
reducing the size of entrance holes3. Thus, losses of
young due to predators are quite low and very few nests
are deserted. Overall, breeding success at this colony
was 0.98 chicks per nest in 2015, slightly above the long-term
average of 0.94 (1986-2015), although this has lessened in
recent years. The reason for the decline in success is uncertain
and is currently an area of investigation4.
These breeding success data are higher than at another small colony
in Belfast Harbour, where only 0.53 young per pair were
fledged between 2000 and 2009 (when black guillemots last attempted
to breed at the site).

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

N/a

3,367

% change since previous
census

N/a

N/a

N/a

Breeding abundance

Seabird 2000 was the first national census to record numbers of
pre-breeding adult black guillemots in a systematic way in the
Republic of Ireland. Counts carried out in April and early May
recorded 3,367 individuals. Few colonies are currently monitored
during the recommended month (April), or at the recommended time of
day (the first few hours after dawn), so the status of the national
population is not known.

Productivity

The productivity of black guillemots in the Republic of
Ireland shows no statistically significant variation over time. On
average, black guillemots fledged 1.22 chicks per pair per year at
the only colony monitored, on Rockabill (Co. Dublin), between 2000
and 2014. No productivity data was submitted to the SMP in
2015.

.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

N/a

4,541

% change since previous
census

N/a

N/a

N/a

Breeding abundance

With no surveys done in the Republic of Ireland during the first
two national censuses, the long-term trend in the black guillemot
population for the whole of Ireland is unknown. However, numbers in
Northern Ireland more than doubled between the Seabird Colony
Register and Seabird 2000. The population for the whole
of Ireland during Seabird 2000 was 4,541 individuals.
Since then, very few colonies have been monitored during the
recommended month (April), or at the recommended time of day (the
first few hours after dawn), so no conclusions can be drawn as to
current population trend for the whole of Ireland. However, in
Northern Ireland, numbers appear to have been relatively stable
during the years since Seabird 2000. Survey work at 14 colonies in
April 2013 recorded 892 individuals, which was similar to
927 individuals recorded at the same colonies during Seabird
20001. Further extensive survey work was carried
out at 36 colonies in April 20142. The total
recorded, at 908 individuals, was 8% fewer than 990
individuals recorded in the same areas during Seabird 2000. There
was evidence that a distributional shift had occurred during the
intervening years. For example, in 2013, numbers in Co. Down had
increased (from 149 to 333) in contrast to a decline in Antrim (278
to 159)1 and, in 2014, 102 birds were recorded at
sites which apparently held no birds during Seabird 2000.

Productivity

The productivity of black guillemots throughout Ireland
showed no statistically significant variation over time. On
average 1.06 chicks were fledged per pair per year at
monitored colonies between 1986 and 2014. No productivity data was
submitted to the SMP from either country in 2015.

Population estimates and change 1969-2002 (census data)

Operation Seafarer

(1969-70)

Seabird Colony Register

(1985-88)

Seabird 2000

(1998-2002)

Population estimate (Individuals)

N/a

303

602

% change since previous
census

N/a

N/a

+99

Breeding abundance

Between the Seabird Colony Register and Seabird 2000 the numbers
of black guillemots on the Isle of Man almost doubled from 303 to
602 individuals. Very little monitoring has been carried out
since then, so the current status of the species is largely
unknown.

Productivity

No systematic data on the productivity of black guillemots on
the Isle of Man have been submitted to the SMP.

Black guillemot does not breed on the Channel
Islands.

UK phenology, diet, survival rates

Phenology

Figure 1: Median date of laying of
the first egg of black guillemots nesting at North Pier, Bangor
Marina (Co. Down), 1986-2014. Reproduced with kind permission
of J. Greenwood.

Detailed study of black guillemots nesting at Bangor Marina has
allowed data on the date of laying of the first egg to be
collected. In 2014, the median date of laying for the first egg was
26th May. From Figure 1 it can be seen that 2014 was a late year
for the onset of egg-laying. There is evidence that the onset of
egg-laying is associated with seawater temperature with warmer
springs bringing the date forward5. On average, it was
calculated that the breeding season became earlier by 2.5 days for
every 1°C increase in April sea-surface temperature.

Diet

No systematic data on black guillemot diet have been
collected as part of the SMP.

Partners

Data have been provided to the SMP by the generous contributions
of its partners, other organisations and volunteers throughout
Britain and Ireland. Partners to the SMP are: BirdWatch Ireland;
The British Trust for Ornithology; Centre for Ecology and
Hydrology; Natural Resources Wales; Department of Environment,
Food and Agriculture (Isle of Man); Department of Environment,
Heritage and Local Government (Republic of Ireland); States of
Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage;
The National Trust; National Trust for Scotland; Natural England;
Northern Ireland Environment Agency; The Royal Society for the
Protection of Birds; Scottish Natural Heritage; Seabird Group;
Shetland Oil Terminal Environmental Advisory Group; Scottish
Wildlife Trust. More about the SMP partners >>